Teachers should be careful to avoid delivering lessons on anorexia and self-harm that act as little more than a set of how-to instructions for vulnerable young people, new guidance warns schools.
Children as young as 5 should also be taught the importance of not keeping adults' secrets, and learn about the ways in which people's bodies can be hurt.
The government-funded guidance for teachers offers advice on the best ways to teach and promote good mental health and emotional well-being in pupils, amid concerns of growing problems among young people.
At key stage 1, teachers are called on to ensure that pupils know "the difference between secrets and surprises, and the importance of not keeping adults' secrets". Children should also be aware that "people's bodies and feelings can be hurt".
Young children should be taught to describe "good and not-sogood feelings", as well as being equipped with simple strategies to manage feelings around change and loss. They are also to be given basic training on how to remain safe online. By key stage 2, pupils should begin to discuss these issues in greater depth.
`Do not provide detailed methods'
Jenny Barksfield of the PSHE Association, which drew up the guidance, said: "There's increasing evidence of younger and younger people with mental health issues. Children are under huge pressure. They're coping with family breakdowns and different issues at home.
"We need to make sure that children are managing and coping with their lives. It's a bit late if we just come in when they're teenagers. We need to build up the language and skills and strategies a bit at a time."
The guidance recommends that teachers do not discuss eating disorders until key stage 3 and self-harm until key stage 4 - and it offers careful instructions on how to introduce the subjects. "Do not provide detailed methods or instructions," it states.
For example, teachers may talk about someone who, at the height of anorexia, weighed only four stone. Or they may discuss techniques that self-harmers use to conceal any scars. "This can be instructive, rather than preventative," the report states.
"It's giving them something to aim for," Ms Barksfield said. "Young people are saying, `I went home and tried exactly what they said.' "
Often, Ms Barksfield added, PSHE lessons were delivered by teachers with no training in the subject. "With the very best intentions in the world, they have the idea that, if you shock pupils, you will put them off doing something," she said. "That isn't true."
A report published earlier this year criticises the lack of action taken by the government to develop PSHE since Ofsted's 2013 verdict that the subject required improvement in 40 per cent of schools. "The government's strategy for improving PSHE is weak," it states.
Despite the new guidance, Ms Barksfield pointed out that the subject itself remained optional. "Whatever we produce, it's still a non-statutory subject," she said.
`Shock won't work'
Mary George, of eating disorder charity B-eat, says that "scare tactics don't work".
"Making pupils think twice is the chilling justification we have been given for showing graphic images of starvation," she says.
"Those images we find so shocking don't shock someone with an eating disorder. The drive for control and perfectionism that anorexia thrives on can make the person in its grasp compelled to become the best, the thinnest anorexic - the one who eats the least."